The present invention relates to a photo-electric smoke detector.
In a conventional method of compensating for the smear caused by the dust or nicotine attached on the surface of a light emitter or a photo-detector or the deterioration of the light emitter of a photo-electric smoke detector, a photo-detector for receiving direct light and a photo-detector for receiving scattered light are provided and set to the same output level under a predetermined condition. In this method of setting, the gain of the amplifiers connected to the photo-detectors is regulated.